The Myers-Briggs Type Indicator (MBTI) is one of the most widely used personality typing instruments in the world. It is used in education, career counseling, human resource development and other related service contexts. Measures of a person's modes of perception and judgment, as well as their degree of introversion/ extroversion are tabulated to create a distinctive four-letter profile (e.g. INTP, ESFJ, etc. Briggs-Meyers, 1980). The core of Myers-Briggs Type Indicator recapitulates the structure of concern. In this section, I will briefly review the origins of the MBTI, before describing how the structure of concern operates within it.

The MBTI was developed and refined by Isabel Briggs Myers and others in order to "…make the theory of psychological types described by C. G. Jung… understandable and useful in peoples' lives". (Briggs-Myers & McCaulley, 1985). Carl Jung held that behind the seeming randomness of human behavior, order and consistency can be found by observing basic differences in the way individuals prefer to use their faculties of perception and judgment. Perception is not just limited to sensory processes. It includes all of the ways by which a person becomes aware of happenings in the world, or ideas in thought. Judgment, on the other hand, refers to the process of coming to conclusions regarding what has been perceived. These are the core personality functions of Jungian psychology. Human variability across these functions underlie a host of corresponding differences in peoples values, reactions, motivations, skills and interests.

The MTBI underwent seven rounds of development between 1942 and 1977. Form A of the test was developed by Isabel Myers and Katherine Briggs, and used within a small criterion group of friends and relatives whose Jungian "types" the two researchers could already estimate fairly well, based on long acquaintance. The test items that survived this initial screening (Form B) were administered to progressively larger samples, to weed out invalid or unreliable items. A third round of development was used to disambiguate the test by excluding any items that were highly valid for more than one index. If an item correlated well on both the Extrovert-Introvert index and the Sensing-Intuiting index, for example, it was dropped from the test. The resulting for (Form C) of the test also incorporated more sophisticated statistical weighting of the items, based on prediction ratios (Briggs-Myers & McCaulley, 1985).

For Form D of the Indicator, developed in 1956-1958, the phrasing of the test was refined to use the forced-choice tactic between two key words. New items were tested against larger groups of adults, and for the first time younger test subjects were also sought out - adolescents and children. Statistical analysis of the trial results began to isolate more fine-grained demographic factors such as gender and age. The surviving items became Forms E and F (which was Form E with some additional experimental items added). Form F was published by the Educational Testing Service in 1962. Finally, between 1975 and 1977, a new standardization was carried out, based on new trials and almost 20 years of widespread use of the instrument. The resulting Form G resulted in type-scores that were almost interchangeable with Form F scores, indicating the maturity of the instrument. Breaking down Indicator profiles by profession made it possible to use Indicator to match up personality types with job categories. The research and analysis behind the occupational typing was also quite rigorous.

The MBTI is not a tool for measuring things about people, it is a tool for sorting people. Its purpose is categorization, not quantification. At the core of the Myers-Briggs Jungian type theory are the four functions: sensing (S), intuiting (N), thinking (T) and feeling (F). These are four essential cognitive processes that everyone uses everyday. However, different people prioritize them differently. We also differ in the attitude - extroverted (E) or introverted (I) - in which we typically use each function.

The Myers-Briggs model is fairly complex. For my purposes, I can restrict my discussion to the four functions, but to do justice to the model, it full extent deserves mention. The four functions are divided into two groups. Sensing and intuiting (SN) form one cluster and thinking/feeling (TF) form the other. These clusters indicate styles for dealing with the outside world. The first cluster (SN) describes Perceiving (P) styles and the second cluster (TF) describes Judging (J) styles.
In MBTI typing, each person is found to have a dominant or preferred function (S, N, T or F). This function is mainly used in the preferred attitude, extroversion or introversion. Extroverts use their dominant function in the external world, and introverts in the inner world of concepts and ideas. Everyone also has a secondary or auxiliary function to balance their primary one. This secondary function operates in the less-preferred attitude (in the inner world for extroverts, in the outer world for introverts - introverts show the outer world their second-best side!). The secondary function will not be in the same cluster as the dominant function. This balances a person’s style, e.g. the secondary function operates in the perception cluster for judgment-dominant people, and vice versa.

The JP preference indicated at the end of the four-letter profile points out the style people used in the Extroverted attitude. This is true for both extroverts and introverts. Also, whichever attitude (E/I) the dominant function (S/N, T/F) expresses itself in, the three non-dominant functions will typically express themselves in the opposite attitude. The function opposed/subordinated to the dominant is usually the weakest. It's called the fourth function. The function opposite to the second/auxiliary is the third function.

The four functions direct conscious mental activity towards different goals, described below:P - Sensation (S) seeks the fullest possible experience of what is immediate and real.E - Intuition (N) seeks the furthest reaches of the possible and imaginable.A - Thinking (T) seeks rational order and plans according to impersonal logic.I - Feeling (F) seeks reasonable order according to harmony among subjective values.

The Perception Functions: Sensing and Intuiting
Jung called the perceptive functions the irrational functions because they are attuned to the flow of events, and operate most broadly when not constrained by rational direction. Perceptive people of either type are attuned to incoming information. Their attitude is open, curious and interested. From the outside, they appear to be spontaneous, curious and adaptable, open to new events and changes, hoping to miss nothing.

Sensing: Perceptions observable by way of senses. Sensing establishes what exists. Because the senses bring into awareness only what is happening at the present moment, people with a sensing orientation tend to focus on immediate experience and develop present-centered abilities, like enjoying the moment, keen observation, memory for details and pragmatism.

Intuition: Refers to the perception of possibilities, meanings and relationships by way of insight. Jung referred to these as perceptions that come by way of the unconscious, surfacing into consciousness suddenly as a hunch or realization. This permits perceptions that extend beyond the present, into possible futures. N people may get so caught up chasing these possibilities that they lose sight of immediate realities. They develop imagination, creative ability, theoretical, abstract, future-oriented…

The Judgment Functions: Thinking and Feeling
These are the rational functions, directed towards bringing life events into harmony with reason. Judging people are concerned with making decisions, seeking closure, planning operations or organizing activities. They tend to shut off once they have absorbed enough information to make a decision. Perceivers will suspend judgment to observe more. Judgers seem organized, purposeful and decisive.

Thinking: Links functions together by making of logical connections. Thinking relies on relationships of cause and effect (dependencies) and tends to be impersonal. Analytic ability, principles of justness and fairness, criticality and an orientation to time that is concerned with connections from the past through the present toward the future.

Feeling: The function by which one comes to decisions by weighing relative values and the merits of the issues. Feeling relies on an understanding of personal values and group values; it is thus more subjective than thinking. Because values are subjective and personal, persons making judgments with the feeling function are more likely to be attuned to the values of others as well as their own. Because people oriented towards feeling make decisions by attending what matters to others, they have an understanding of people, a concern with the human as opposed to the technical aspects of problems, a need for affiliation, a capacity for warmth, a desire for harmony, and a time orientation that includes preservation of the values of the past.

Procrastination comes from Perception with a deficit of Judgment. Prejudice comes from Judgment with a deficit of Perception.